The utilisation of both glass fibre and polymer waveguides in optical methods of monitoring and detecting deformations within structural materials is well documented. To detect material failures, optical fibres are normally bonded to various locations on the surface of structures or embedded in the matrix of a composite materials such that when cracks or significant deformations occur in the said material the optical fibre's break at the position of deformation on the surface of or within the structure. By utilising optical time domain reflectometry techniques the positions of the fibre fractures can be calculated and thus the active monitoring and measurement of specific material failure characteristics is possible.
The major drawback with the current methods of crack detection utilising optical fibres is that once the test fibre has broken no further information relating to events any further along the fibre path can be recorded and subsequently the fibre must be replaced to resume analysis.